The tach on my 93 will drop to zero and immediately recover when I turn on my turn signal. What would cause this?

 

Loss of voltage or ground to your tach

What have you checked so far??

Anything else not working

Charging system working like it should??

 

Everything else is working fine as is the charging system haven't tried anything yet and frankly at a loss on where to start. Was hoping someone else had encountered this before and could point me in the right direction.

 

My '94 DLX 4x4 hasn't done this in a long time (8 months or so), but has never consistently had the issue even at it's most frequent times. Oh and mine's on the speedo, not the tach.

https://jimsgarage.wordpress.com/201...uncing-speedo/

But according to that guy, replacing his turn signal flasher fixed the problem. Something to do with the logic reversing device inside of it, which I'm not sure if he was saying that the new one did away with that electro-mechanical design altogether by using something with no physical moving parts (like a MOSFET or something), or just the fact that it was new and thereby not old enough to be problematic or something.

Also, just in case it helps with sorting out what the issue is, I swapped an SR5 gauge cluster into my DLX a year ago and the speedometer would still do this, perhaps more rarely.

 

We got it guys. The ground wire from the head to the firewall was loose. Thank You all for your help.
Bill